1. Field of the Invention
This invention relates generally to vehicle driving aids and more particularly to an improved reflective pavement marker for vehicle roadways and the like.
2. Discussion of the Prior Art
Motor vehicle roadways, such as highways, freeways, and surface streets are commonly provided with traffic lanes defined by some type of readily visible lane defining or dividing means. In some cases, simple painted lines are used. Most frequently on major roadways reflective pavement markers are used because of their superior visibility, particularly at night, and their ability to alert a dozing driver by virtue of the sound and vibration produced upon passage of vehicle wheels across the markers. This invention is concerned with such pavement markers.
In essence, a reflective pavement marker comprises a generally flat and relatively thin marker body, referred to herein as a marker button, to be bonded or otherwise secured to a vehicle roadway and light reflectors or other light reflective means on the button for reflecting light from the headlights of approaching vehicles back toward the vehicles. A vast assortment of such pavement markers have been devised. Of interest in this regard are U.S. Pat. Nos. 1,906,655 and 3,332,327.
Reflective pavement markers of this kind present two major problems to which the present invention is addressed. One of these problems resides in the fact that many of the light reflectors used on such markers are prone to rapid physical and/or optical degradation, and hence loss of their light reflecting capability, by repeated contact by the wheels of passing vehicles.
One prior art solution to this problem involves the use of light reflectors which are specially designed to withstand such wheel contact without damage or appreciable optical degradation or which are effectively self cleaning by the action of passing vehicles. Such reflectors, however, tend to be quite complex and costly and thus are ill-suited to use in pavement markers from the standpoint of cost effectiveness. According to another prior art solution to the problem which avoids the above disadvantages of complexity and cost, the reflectors are recessed into the marker button in such a way that vehicle wheels roll over the button without contacting the reflectors. This latter solution, however, gives rise to the second problem referred to above.
Thus, the reflector recesses of the existing recessed reflector type pavement marker are essentially channels which are open only at one end, that is the end facing the approaching vehicle traffic, and which are bounded at their opposite end by an end wall mounting a reflector and along their sides by side walls extending from the end wall to the perimeter of the marker button. Such an essentially closed channel-like recess has two interior corners and tends to collect dirt and other debris which soon covers and obscures the reflector and thus greatly reduces the night-time effectiveness of the marker. Moreover, the drafts created by passing vehicles are not effective to blow such debris from the recess, nor is rain effective to wash away the debris.